Marion County’s Sensitive Groundwater Overlay (SGO) program was created to implement the groundwater resources' goals and policies of the Environmental Quality and Natural Resources section of the Marion County Comprehensive Plan. Marion County Code 17.181 (the Rural Zone Code’s Sensitive Groundwater Overlay Zone Chapter) implements this program by reviewing land use applications to assess the risk that a proposal will adversely affect the sustainability of aquifer production in a specific area. This program is not intended to act as a guarantee that a property owner will successfully locate an adequate water supply at a particular location or on a specific lot or parcel, or that any individual well will continue to provide adequate water for an existing land use.

The following are links to information and documents related to the Sensitive Groundwater Overlay program:

Chapter 181 of the Marion County Rural Zone Code requires applicants for certain developments submit evidence of the long-term sustainability of groundwater resources in the vicinity of the new development. Residential land divisions (partitions and subdivisions) and non-residential developments (commercial or industrial) proposed within the SGO boundaries that use water from non-exempt wells must comply with the requirements of the overlay zone.

Marion County provides the Hydrogeology Reviews and Studies Manualto expan­d upon the Zone Code requirements, and provide a format for registered geologists and engineering geologists hired by land-use applicants to complete required analyses and reports.

The following are samples of maps and diagrams mentioned in the Hydrogeology Reviews and Studies Manual that may be required.

Marion County's "Water Plan".The "Geologic and Hydrogeologic Study of the Residential Acreage-Zoned Areas of Marion County Underlain by the Columbia River Basalt and Older Rocks" was prepared in 1997 by Northwest Geological Services, Inc. This study compiled existing groundwater and geologic studies for a 144 square mile area of Marion County. The purpose of the study was to evaluate the information for portions of Marion County that were, at that time, zoned Acreage Residential and obtained water from aquifers in the Columbia River Basalt and/or underlying strata. The Study then identified the amount of groundwater resource presently consumed, additional resource available for future development, areas where the groundwater resource was apparently being depleted by existing uses, areas where the groundwater resource could be depleted by completion of approved build out, and recommend limitations necessary to protect the resource for present residents.

This is a very large document with large-sized maps and diagrams. Contact our office if you would like to obtain a copy of the plan or associated exhibits, maps, etc.